Why this topic matters: Kidney stones can cause severe renal colic, vomiting, haematuria and urinary obstruction. Most small uncomplicated stones pass, but an infected obstructed kidney, solitary kidney obstruction, bilateral obstruction, anuria, uncontrolled pain or acute kidney injury can become life-threatening. EMT students must separate uncomplicated colic from sepsis, ectopic pregnancy, abdominal catastrophe and obstructive uropathy requiring urgent decompression.
Learning objectives
- Explain stone formation, movement and the typical pattern of renal colic.
- Recognise red flags for infected obstruction, AKI, anuria and alternative emergencies.
- Perform focused history, examination, urine testing, blood tests and appropriate imaging.
- Describe analgesia, antiemetics, fluids, antibiotics, urology referral and definitive treatment.
- Provide prevention, stone analysis, dietary advice and follow-up education.
Definition and pathophysiology
Kidney stones are crystalline deposits formed when urine becomes supersaturated with substances such as calcium, oxalate, phosphate, uric acid or cystine. A stone may remain in the kidney without symptoms or move into the ureter. Stretching and spasm of the ureter produce colicky pain; obstruction increases upstream pressure and can impair renal function. A stone plus infection is a dangerous combination because bacteria may be trapped behind the obstruction.
Stone risk is increased by low urine volume, heat and dehydration, high salt intake, metabolic disorders, recurrent urinary infection, family history, obesity, certain medicines and anatomical abnormalities.
Typical presentation
| Feature | Typical pattern | Important caution |
|---|---|---|
| Pain | Sudden severe flank/back pain radiating to groin or genital area; patient may be unable to keep still. | Constant pain, peritonism or pain out of proportion needs alternative diagnosis. |
| Urinary symptoms | Frequency, urgency, dysuria or inability to pass urine when stone is distal. | Fever/dysuria may indicate infected obstruction. |
| Haematuria | Pink, red, brown or microscopic blood. | Absence of haematuria does not exclude a stone; visible blood has other serious causes. |
| Gastrointestinal symptoms | Nausea, vomiting, sweating and restlessness. | Persistent vomiting causes dehydration and AKI. |
| Infection signs | Fever, rigors, chills, tachycardia, hypotension or confusion. | Obstructed infected kidney is a urological emergency. |
Red flags requiring urgent escalation
- Fever, rigors, sepsis, immunosuppression or a toxic appearance.
- Anuria, very low urine output, rising creatinine or hyperkalaemia.
- Solitary kidney, renal transplant, bilateral obstruction or known CKD.
- Uncontrolled pain or vomiting despite treatment.
- Pregnancy, child, older frail patient or diagnostic uncertainty.
- Peritonism, pulsatile abdominal mass, syncope, vaginal bleeding, testicular pain or suspected ectopic pregnancy.
Triage and first contact
- Assess ABCDE, pain score, temperature, pulse, BP, hydration, urine output and sepsis signs.
- Ask onset, radiation, previous stones, fever, dysuria, urine output, pregnancy possibility, medications and renal history.
- Check for abdominal, vascular, gynaecological, testicular and spinal alternatives.
- Establish IV access for severe pain/vomiting or instability; collect urine and blood tests early.
- Pre-alert urology for suspected infected obstruction or anuria; do not discharge while awaiting deterioration.
Focused examination
- Observe restlessness, pallor, sweating, dehydration, fever and toxic appearance.
- Check flank/CVA tenderness, abdominal tenderness, guarding, rigidity, bowel sounds and pulsatile mass.
- Assess genital/testicular findings when indicated and perform pregnancy assessment in reproductive-age patients.
- Check lungs and heart for fluid status, sepsis or alternative cardiopulmonary disease.
- Record urine output and inspect for catheter obstruction or retention.
Investigations
| Investigation | Purpose | Clinical point |
|---|---|---|
| Urine dipstick/microscopy and culture | Detect blood, leucocytes, nitrites, protein and infection. | Culture suspected infection; pyuria with obstruction is high risk. |
| FBC, CRP, renal profile/electrolytes | Assess infection, AKI, dehydration and metabolic complications. | Rising creatinine or potassium requires urgent renal/urology input. |
| Pregnancy test | Guide imaging and differential diagnosis. | Consider ectopic pregnancy and use ultrasound when pregnant. |
| Ultrasound | Detect hydronephrosis, obstruction, bladder retention and pregnancy-safe findings. | First-line in pregnancy and commonly in children. |
| Low-dose non-contrast CT | Confirm stone size/location and alternative diagnosis in adults. | Use urgent local pathway; do not delay treatment of sepsis or shock. |
| Stone analysis/metabolic urine studies | Identify recurrence risk and prevention plan. | Arrange after acute episode through urology/renal follow-up. |
Analgesia and symptom control
- Use the local renal-colic protocol. NSAIDs are often first-line when renal function, hydration, bleeding risk, allergy, pregnancy and gastrointestinal status permit.
- Use paracetamol or prescribed opioid analgesia when NSAIDs are contraindicated or inadequate; monitor sedation and breathing.
- Give antiemetics for vomiting and reassess hydration and electrolyte status.
- Avoid giving large volumes of fluid simply to “force” a stone through; replace dehydration carefully and monitor obstruction/overload.
- Document pain score before and after treatment, dose, route, response and adverse effects.
Infected obstructed kidney
Fever or sepsis with a blocked ureter is an emergency. Antibiotics alone may not sterilise an obstructed system. Treat sepsis immediately, obtain cultures where feasible and arrange urgent drainage by ureteric stent or nephrostomy under urology.
- ABCDE, sepsis assessment, oxygen for hypoxaemia and IV access.
- Blood/urine cultures without delaying broad-spectrum antibiotics according to local protocol.
- Carefully reassessed fluids, lactate/urine monitoring and vasopressors in critical care when shock persists.
- Urgent imaging and urology consultation for decompression; definitive stone removal usually waits until infection is controlled.
- Monitor for AKI, hyperkalaemia, respiratory failure and septic shock.
Definitive treatment and referral
- Small stones likely to pass may receive observation, analgesia, antiemetics and selected medical expulsive therapy under urology guidance.
- Ureteroscopy, shock-wave lithotripsy or percutaneous nephrolithotomy may be used according to size, location, obstruction, infection and local resources.
- Persistent intolerable pain, unlikely passage, obstruction, infection, impaired renal function or a solitary kidney need urgent specialist decision.
- Collect a passed stone when possible for composition analysis; recurrence prevention depends on stone type and metabolic risk.
Nursing interventions and monitoring
- Record pain, vital signs, temperature, urine output, nausea/vomiting, hydration and response to every medicine.
- Strain urine only when requested and preserve a passed stone safely for analysis.
- Maintain IV access, reassess lungs after fluids and monitor renal function/electrolytes.
- Observe for fever, rigors, hypotension, confusion, anuria or worsening pain and escalate immediately.
- Prepare patients for imaging, stent/nephrostomy, lithotripsy or surgery; provide privacy and clear explanations.
- Teach hydration and medication instructions without encouraging unsafe overhydration during obstruction.
Prevention and lifestyle
- Maintain adequate fluid intake across the day, especially in hot climates, unless a clinician has prescribed fluid restriction.
- Reduce excessive salt and follow stone-specific dietary advice; do not eliminate dietary calcium without specialist advice.
- Moderate animal protein and high-oxalate foods when indicated by stone analysis.
- Manage obesity, gout, hyperparathyroidism, recurrent infection and bowel disease.
- Review medicines that increase stone risk and arrange metabolic evaluation for recurrent, bilateral, childhood or complicated stones.
Complications
| Complication | Clues | Response |
|---|---|---|
| Infected obstruction | Fever, pyuria, rigors, hypotension or confusion. | Sepsis care, antibiotics and urgent drainage. |
| Acute kidney injury | Oliguria, anuria, rising creatinine or potassium. | Renal profile, ECG and urgent urology/renal review. |
| Hydronephrosis | Persistent obstruction, flank pain or ultrasound dilation. | Urology referral and decompression decision. |
| Medication toxicity | GI bleeding, bronchospasm, AKI, sedation or hypotension. | Stop/review medicines and treat adverse effects. |
| Misdiagnosis | Peritonism, vascular collapse, ectopic pregnancy or testicular torsion. | Broaden differential and activate the relevant emergency pathway. |
Clinical scenarios
Scenario 1 – Uncomplicated colic: A stable adult has flank-to-groin pain, microscopic haematuria, no fever and normal renal function. Treat pain/nausea, arrange appropriate imaging and follow-up, and provide strict return precautions.
Scenario 2 – Infected obstruction: A patient with a known ureteric stone has fever, rigors, tachycardia and reduced urine. Start sepsis care and antibiotics, obtain cultures, and arrange urgent urological decompression.
Scenario 3 – Pregnancy: A pregnant patient has severe flank pain and vomiting. Assess maternal stability, urine and infection, use ultrasound first and involve obstetric/urology teams.
Common errors to avoid
- Discharging a febrile patient with an obstructed stone after analgesia alone.
- Giving excessive IV fluids to force stone passage.
- Using NSAIDs without checking AKI, dehydration, pregnancy, bleeding or allergy risk.
- Ignoring anuria, solitary kidney or rising creatinine.
- Assuming every flank pain is renal colic without considering ectopic pregnancy, AAA, appendicitis, torsion or pyelonephritis.
- Failing to provide return precautions and stone-prevention follow-up.
STONE SAFE: S – Sepsis and shock; T – Time pain/onset; O – Output and obstruction; N – NSAID safety; E – Examine alternatives. S – Scan appropriately; A – Analgesia/antiemetic; F – Follow-up; E – Escalate infected obstruction.
Revision questions
- Why is an infected obstructed kidney a urological emergency?
- Describe typical renal-colic pain and list important alternative diagnoses.
- What tests are required in a patient with suspected renal colic?
- When are ultrasound and non-contrast CT preferred?
- What factors make NSAIDs unsafe?
- What signs require urgent urology/renal referral?
- Write discharge teaching for recurrent kidney stones.
Key takeaways
- Most uncomplicated small stones pass, but infection plus obstruction is life-threatening.
- Assess sepsis, renal function, urine output, pregnancy and alternative emergencies.
- Give effective analgesia and antiemetics while arranging appropriate imaging.
- Do not delay antibiotics or decompression in infected obstruction.
- Prevention requires stone analysis, hydration and personalised metabolic advice.